lib/kasprintf.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/lib/kasprintf.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 #include <linux/stdarg.h>
   9 #include <linux/export.h>
  10 #include <linux/slab.h>
  11 #include <linux/types.h>
  12 #include <linux/string.h>
  13
  14 /* Simplified asprintf. */
  15 char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
  16 {
  17         unsigned int first, second;
  18         char *p;
  19         va_list aq;
  20
  21         va_copy(aq, ap);
  22         first = vsnprintf(NULL, 0, fmt, aq);
  23         va_end(aq);
  24
  25         p = kmalloc_track_caller(first+1, gfp);
  26         if (!p)
  27                 return NULL;
  28
  29         second = vsnprintf(p, first+1, fmt, ap);
  30         WARN(first != second, "different return values (%u and %u) from vsnprintf(\"%s\", ...)",
  31              first, second, fmt);
  32
  33         return p;
  34 }
  35 EXPORT_SYMBOL(kvasprintf);
  36
  37 /*
  38  * If fmt contains no % (or is exactly %s), use kstrdup_const. If fmt
  39  * (or the sole vararg) points to rodata, we will then save a memory
  40  * allocation and string copy. In any case, the return value should be
  41  * freed using kfree_const().
  42  */
  43 const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list ap)
  44 {
  45         if (!strchr(fmt, '%'))
  46                 return kstrdup_const(fmt, gfp);
  47         if (!strcmp(fmt, "%s"))
  48                 return kstrdup_const(va_arg(ap, const char*), gfp);
  49         return kvasprintf(gfp, fmt, ap);
  50 }
  51 EXPORT_SYMBOL(kvasprintf_const);
  52
  53 char *kasprintf(gfp_t gfp, const char *fmt, ...)
  54 {
  55         va_list ap;
  56         char *p;
  57
  58         va_start(ap, fmt);
  59         p = kvasprintf(gfp, fmt, ap);
  60         va_end(ap);
  61
  62         return p;
  63 }
  64 EXPORT_SYMBOL(kasprintf);